The present invention relates to an anchoring dowel in general, and more particularly to an anchoring dowel made of synthetic plastic material.
There are already known anchoring dowels of various constructions, among them such into which threaded elements, such as screws, are threaded when the anchoring dowel is received in an anchoring hole of a support structure to which an object is to be attached by means of the anchoring dowel and of the screw threaded thereinto. Such dowels are to be used in support structures of various thicknesses so that, depending on the thickness of the particular support structure, the anchoring dowel is either fully received in the support structure, or the leading end thereof projects beyond the rear major surface of the support structure and engages behind the same. The anchoring dowels of this construction have spreading portions either commencing at the leading end of the anchoring dowel, or located in the central region of the anchoring dowel intermediate the leading and trailing ends thereof, such spreading portions or sections being separated from one another by slots which are usually straight and extend in the longitudinal direction of the anchoring dowel.
It is well known that the dowel of the above-discussed construction, when received in the anchoring hole of the support structure, has a tendency to be entrained by the screw or other threaded element being threaded thereinto for joint turning therewith, rather than remaining stationary in the anchoring hole and thus permitting the threading of the threaded element into the internal passage of such anchoring dowel. To avoid this possibility of entrainment, it has already been proposed to equip the anchoring dowels with detent lugs which engage the support structure at the anchoring hole and keep the anchoring dowel stationary relative to the support structure. Thus, it has already been proposed to equip the anchoring dowel with outwardly projecting resilient lugs which are yieldably connected to the body portion of the anchoring dowel and engage the surface bounding the anchoring hole in the support structure. In this connection, it is also already known to let the detent lugs extend from the body portion in the longitudinal and circumferential direction of the body portion, and particularly in the direction of threading of the threaded element into the internal passage of the anchoring dowel.
It has also already been proposed, for instance, in a German Utility Patent DT-GBM 19 64 527, to manufacture the anchoring dowel in one piece with the projecting detent lugs from synthetic plastic material in an injection molding process. This anchoring dowel has approximately triangular wings which are arranged at the border of the slot which separates the spreading sections from one another. When the threaded element, such as a screw, is being threaded into the internal passage of the dowel, the attendant loading of these wings can easily result in a deformation of the spreading sections, which can then result in an impairment of the guidance of the threaded element during the threading thereof into the internal passage of the anchoring dowel. Furthermore, anchoring dowels of this type are not suited for use in thin-walled support structures in which the leading end of the anchoring dowel extends beyond the support structure, nor do they readily lend themselves to the considerably force-resistant dimensioning of the wings.
On the other hand, there is also already known a spreadable anchoring dowel disclosed, for instance, in the German Patent DT-PS 1 909 098 which has an internal passage of diminishing transverse dimensions toward the leading end of the anchoring dowel into which a connecting screw or the like can be threaded, such anchoring dowel having, over a part of its length, separate spreading sections. This anchoring dowel is further equipped with resiliently yieldable detents which extend outwardly beyond the outer circumference of the body portion of the anchoring dowel in their relaxed condition. Such detents are elastically connected, at one longitudinal side of each, with the body portion of the anchoring dowel, and each of the detents extends substantially tangentially of the body portion and in the threading direction of the threaded element. The region of the detent which is closer to the leading end of the body portion conforms to the circumferential shape of the body portion, and the detent extends from there both in the direction to the trailing end of the body portion and in the direction of threading of the screw, gradually increasing in distance from the body portion in these directions. The anchoring dowel of this type, or the body portion thereof, has a depression which is capable of accommodating at least a part of the respective detent in a deformed position thereof. The respective detent of this anchoring dowel is shaped as a substantially rectangular lug which is delimited by slits extending substantially transversely of the longitudinal axis of the body portion and separating the lugs from the latter. The respective lug is yieldably connected to the body portion at its merger region which is located at that side of the lug which faces opposite to the threading direction, the lugs being arranged centrally on the spreading sections in the region of the converging region of the internal passage of the body portion. This detent lug, when in its relaxed position, has its end face that faces in the threading direction increase in distance toward the trailing end of the anchoring dowel, and its end which face toward the trailing end of the anchoring dowel also increase in distance in a gradual fashion so that these two faces bound a corner region which, in the relaxed position, extends outwardly beyond the generally cylindrical contour of the body portion of the anchoring dowel. A pocket-shaped depression is arranged underneath the detent lug, the depression being capable of fully accommodating the detent lug over its entire circumference, the bottom surface of this depression, related to the transverse direction of the dowel, extending substantially parallel to the longitudinal central plane of the slot of the dowel as well as, related to the axial direction of the dowel, inclinedly to the leading end of the anchoring dowel.
While the dowel of this type performs its function to satisfaction in most circumstances and particularly avoids the drawbacks which have been discussed above in connection with the first-discussed anchoring dowel, it still leaves much to be desired, particularly since it is not suited for all applications, it is quite difficult to manufacture and thus expensive, and it is quite difficult to introduce it into the anchoring hole of the support structure.